Multi-mode powertrain systems may include an internal combustion engine (engine) and one or more non-combustion torque machines that generate torque that is transferred through a gear train to a driveline for propulsion when employed on a vehicle. Such powertrain operation may include operating with the engine in either an ON state or an OFF state, wherein operating with the engine in the ON state may include operating the engine to charge an on-board energy storage device that provides power that is consumed by one of the non-combustion torque machines to generate propulsion effort. The engine may operate at speed/load operating points that may generate audible noise and discernible vibrations that are objectionable to passengers or the vehicle operator.